Conventionally, this kind of surface acoustic wave device realized the reduction in size and height by forming a solder bump on the upper surface of an alumina mounting substrate, coupling a surface acoustic wave element to the mounting substrate via the solder bump with a surface for propagating a surface wave facing downward, and then coating the periphery of the surface acoustic wave element with a sealing resin layer.
A conventional surface acoustic wave device described in, for example, Japanese Patent Unexamined Publication No. H8-204497 includes sealing resin 1, mounting substrate 2, solder bump 3, and surface acoustic wave element 4 as shown in FIG. 3A.
However, in a conventional configuration, bump 3 used for coupling surface acoustic wave element 4 and mounting substrate 2 is formed of only a solder material. An exterior is also formed of only a resin layer. Therefore, when a strong pressure is applied from the outside, bumps are largely crushed as shown in FIG. 3B, which may lead to problems in electrical characteristics, for example, an open-circuit fault, a short-circuit fault, and the like.